1. Field of the Invention
The present invention relates to a projection exposure apparatus for producing semiconductor circuit devices such as integrated circuits, large-scale integrated circuits, very-large-scale integrated circuits etc., and more particularly to a printing apparatus utilizing a projection optical system for projecting an entire image or a partial image of a mask onto a wafer. The apparatus is adapted to displace the mask and wafer as a unit or either one thereof relative to said projection optical system thereby projecting the image of the mask onto the wafer.
2. Description of the Prior Art
An exposure apparatus capable of forming the image of a part of a mask on a wafer and displacing said image relative to the imaging optical system is already disclosed in the Japanese Patent Laid-Open Sho 54-53867 filed by the present applicant on Oct. 6, 1977. Also already known is a so-called stepper projection exposure apparatus capable of forming a reduced entire image of the mask onto a part of the wafer and stepwise displacing the wafer relative to the mask and the imaging optical system thereby printing a plurality of mask images on said wafer.
In such scanning projection exposure apparatus, the displacing member has to be properly positioned by guide means.
For example in the projection exposure apparatus disclosed in the above-mentioned Japanese Patent Laid-Open Sho 54-53867, a mask support member and a wafer support member integrally connected thereto are movably supported on two guide rails and displaced therealong. Thus if these guide rails are not precisely assembled, the mask and wafer will locally be two-dimensionally inclined relative to the optical system, thus resulting in local aberration of the mask image. For this reason the precision of linearity of two guide rails has to be strictly controlled.